How to read Image files from folder

I have a project where the directories look like this

Java Code:

/src // Where I have all my source-code
/src/org/shockassault/
/src/org/shockassault/graphics/
/src/org/shockassault/input/
/res // Where I have all my images
/res/textures/Simple_Tile.jpg // The file image I want to access

How would I access that image from the /src/org/shockassault/graphics/ (where the class is)? There is a way, but I think it has to do with how I use the Java Compiler (javac) by adding a classpath or something like that.

The reason I ask is that I was following a tutorial, but this tutorial does stuff in Eclipse, and I don't use Eclipse nor to I plan to, and he used a method as such: